That a bit dramatic and dangerous rescue mission under the -- all the captured on video divers in the Pacific Ocean. Risking their life to save a whale -- struggling for its own life. ABC's -- -- tonight with the story from the divers themselves. The morning scuba dive turned into an unexpected rescue mission when divers at 250 miles south of -- -- Lucas. Came upon a thirty foot whale shark in serious trouble. A -- who were overwhelmed so tightly around its body it's cutting into the flash. -- and then there's so long barn animals were building up on it. And I did good canonized -- right it is going good. Experienced dive master Danny's upon -- sprung into action with his pocket knife. As fellow divers looked on anxiously more than -- hundred feet beneath the surface. Actually wasn't difficult and goodfellas -- Qaeda and holiday really the hardest. -- -- -- -- -- -- -- As the rope falls away the gentle giant -- wounded but finally free. Their mission of mercy accomplished. Feel so good. Handed back aboard their -- and and he wouldn't welcome. -- can on me ABC news New York.

This transcript has been automatically generated and may not be 100% accurate.

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